The invention generally relates to the field of window regulators, and more particularly to window regulators for automotive applications.
One of the designs objectives for window regulating systems, particularly in automotive applications where the regulator controls the vehicle window, is to optimize the operating torque by maximizing the number of crank turns to the limit provided for by specification. In automotive applications, the maximum number of permissible crank turns is generally limited in manual applications to about 6-6.5 turns. Reducing the operating torque reduces the amount of power or manual effort required to raise the window.
Conventionally, operating torque can be reduced by reducing the diameter of the drum which connects the crank to the cable(s) attached to the lift plate. The problem with this solution is that the cable is subject to higher stress because it is wrapped around a smaller diameter. In addition, decreasing the diameter of the drum will increase the number of turns, resulting in a wider drum. This could result in packaging problems since the width of the drum and drum housing must fit within a confined space defined between the inner and outer panels of a vehicle door. In addition, increasing the number of drum turns increases the possibility of ratcheting (i.e., noise) resulting from the cable rubbing against the walls of the grooves in the drum, particularly since the cable is routed at a greater angle between its intake position entering the drum housing and the outermost turns of the drum.
An alternative approach to reducing operating torque is to employ a gear reduction system in the drum housing. The problem with this solution is that the extraneous gears typically increase the width of the drum housing, leading to the packaging constraints discussed above. Another problem with gear reduction systems is that they typically require tight tolerances, driving up costs, and backlash is a persistent problem in such systems.
A alternative solution of preferably low cost is desired in order to optimize torque in window regulating systems.
In general, the invention employs a pulley xe2x80x98block and tacklexe2x80x99 principle in order to obtain a mechanical advantage for reducing operating torque requirements.
According to one aspect of the invention, there is provided a window regulator assembly. The window regulator has a rail on which a lift plate is mounted to slide therealong. The lift plate is configured to mountingly receive a window thereto. A lift pulley is rotatably mounted on the lift plate. A first guide pulley and a second guide pulley are respectively mounted near first and second ends of the rail. The assembly has at least one cable that has a first end anchored near the first end of the rail and wound about the lift pulley and thence routed about the first guide pulley to operatively engage a crank assembly, and a second end anchored near the second end of the rail and wound about the lift pulley and thence routed about the second guide pulley to operatively engage the crank assembly. Operative movement of the crank assembly in a first sense tensions the at least one cable to move the lift plate towards the first end of the rail, and operative movement of the crank assembly in a second sense, opposite the first sense, tensions the at least one cable to move the lift plate towards the second end of the rail.
The preferred embodiment employs first and second cables. The first cable is fixed near the first end of the rail, thence wound around the lift pulley to the first guide pulley, and thence routed to the crank assembly. The second cable is fixed near the second end of the rail, thence wound around the lift pulley to the second guide pulley, and thence routed to the crank assembly. The crank assembly preferably includes a multi-turn cable-guiding drum, the first and second cables being anchored to the drum and disposed to wind around the drum.